The present invention relates to the treatment or prophylaxis of cardiac disorders. More particularly, the invention relates to a novel method of treatment or prophylaxis of cardiac disorders which comprises administration of .beta.-adrenergic blocking agents and to compounds useful in such method.
The therapeutic and prophylactic uses of compounds which block sympathetic nervous stimulation of .beta.-adrenergic receptors in the heart, lungs, vascular system and other organs are well documented. Typically, such compounds are administered therapeutically to patients suffering from ischemic heart disease or myocardial infarction for the purpose of reducing heart work, i.e., heart rate and contractile force. Reducing heart work reduces oxygen demand, and may also actually increase oxygen supply. Thus reducing heart work can aid in the prevention of further tissue damage and can relieve angina pectoris.
.beta.-Adrenergic stimulation may also aggravate or cause arrhythmias because of increased levels of catecholamines. Thus .beta.-blocking agents may be employed to reduce the risks of arrhythmias.
Compounds have been discovered which selectively block .beta.-adrenergic receptors in various organs. Beta receptors in the heart are generally referred to as .beta..sub.1 receptors, and those associated with vasodilation and bronchodilation are .beta..sub.2 receptors. Non-selective .beta.-blockers are not preferred for the treatment of cardiac disorders because of their hypertensive action and potential undesirable effects on asthmatic patients. A number of .beta..sub.1 selective adrenergic blocking agents have been discovered. Smith, L. H., J. Appl. Chem. Biotechnol., 28, 201-212 (1978). Most of such compounds are structural variations of 1-amino-3-aryloxy-2-propanol.
Heretofore, the emphasis in .beta.-blocker research has been to develop compounds which can be administered to cardiac patients over long periods of time. However, often it is desirable in the critical care setting to quickly reduce heart work or improve rhythmicity during a cardiac crisis, e.g., during or shortly after a myocardial infarction. Conventional .beta.-blocking agents can be employed for such treatment, but their duration of action may be much longer than desired by the physician. A .beta.-blocking agent possessing a long duration of action does not allow precise control of heart work or prompt reversal of the .beta.-blocking effect, which may be required in a critical care setting. For instance, if heart output becomes dangerously low, it is desirable to quickly reduce or eliminate .beta.-blocking activity. The lingering activity of available .beta.-blocking agents can be counterproductive and can greatly complicate the therapeutic decisions required of the physician during such critical care of cardiac patients.